The present invention relates to a process for producing an aromatic polyester amide.
Heretofore, there are known the following two processes for the production of aromatic polyester amides. According to the first known process, an aromatic polyester amide is produced by reacting an aromatic dicarboxylic acid or a derivative thereof with an aromatic dihydroxyl compound and an aromatic diamine. The process, however, is disadvantageous in that it is very difficult to establish an optimum condition for producing the copolymer with good reproducibility, because two reactions, that is, the reaction of acid halide and amino group and the reaction of acid halide and phenolic hydroxyl group, which are quite different in the reaction rate, are involved in the polymerization reaction.
The second known process involves the reaction of an aromatic dicarboxylic acid or a derivative thereof and an aromatic hydroxylamino compound for the production of an aromatic polyester amide represented by the following formula. (Japanese Patent Publication No. 46-37739 [1971]) ##STR1## (where R.sub.1 and R.sub.2 denote hydrogen, alkyl group of C.sub.1 to C.sub.3, or chlorine or bromine atom; R.sub.3 denotes hydrogen, alkyl group of C.sub.1 to C.sub.4, or aryl group of C.sub.6 to C.sub.12 ; Ar denotes p- or m-phenylene group, or diphenylene, diphenyl alkylene, diphenyl ether, or diphenyl sulfide group; X denotes a single bond, alkylene or isoalkylene group of C.sub.1 to C.sub.5, cycloalkylene group of C.sub.5 to C.sub.12, or oxygen or sulfur atom; n is 0 or 1; and z is an integer of 5 or over.)
The polymer obtained by this second process has preferable properties, but it also has the following drawbacks.
(1) It dissolves in chlorinated solvents such as methylene chloride, chlorobenzene, and chloroform. Therefore, it is poor in resistance to chlorinated solvents.
(2) The softening point is lower than 240.degree. C.
(3) It is difficult to invariably obtain the polymer of high molecular weight because the growth of the polymer stops due to the hydrolysis of the active terminals of the growing polymer. This hydrolysis takes place because the polycondensation is accomplished by bringing two solutions into contact with each other--a solution of aromatic hydroxyamino compound and aromatic dicarboxylic acid dichloride dissolved in an organic solvent and an aqueous solution of acid-acceptor, and water in the aqueous solution dissolves into the organic solvent phase.
According to the known process as disclosed in the abovementioned Japanese Patent, the polymerization degree is greatly affected by the time required for charging the raw materials, because the polymerization is carried out by interfacial contact of two solutions--an organic solvent solution of hydroxyphenyl-aminophenyl-propane and aromatic dicarboxylic acid dihalide and an aqueous solution of acid-acceptor. If a polymer of high molecular weight is to be produced, the hydroxyphenyl-aminophenyl-propane and the aromatic dicarboxylic acid dihalide have to be charged exactly in equimolar amounts at the beginning of reaction. It is impossible to adjust the molecular weight by adding the raw materials during polymerization. Therefore, this process is not suitable for large-scale industrial production.
Although aromatic polyesters and aromatic polyamides have long been known, they have their merits and demerits. The former is superior in moisture absorption characteristics and wet heat resistance, but poor in thermal stability and moldability. On the other hand, the latter is superior in heat resistance but is poor in moisture absorption characteristics and moldability.
The aromatic polyester amide having both amide bonds and ester bonds is expected to be a promising polymer having the merits of both aromatic polyester and aromatic polyamide.